This application is in English. The invention concerns a toothed rotor set for a pump, especially for a lubricating oil pump for internal combustion motors. The toothed rotor is similar to a toothed ring pump with toothed construction whereby the function and mode of action of a toothed rotor set corresponds to that of a toothed ring pump.
With toothed ring pumps, the pressure chamber is not separated from the suction chamber by a sickle-shaped filling element, but rather a special construction of the teeth-based upon trochoid gearing-guarantees the sealing between toothed ring and outer geared pinion. The internal geared toothed ring possesses one gear more than the pinion so that with corresponding configuration of the gears, the gear tips touch precisely over against the gear engaging point. In order that a rolling off is guaranteed, a tip play between the gear tip of the outer rotor and gear tip of the internal rotor must be present. The disadvantage of toothed ring pumps is that, owing to this tip play, internal leakages and consequently a poor volumetric degree of efficiency occurs. Owing to this, no high pressures can be built up at low rotational speeds.
More advantageous in comparison with toothed ring pumps is a pump according to the theory of DE-A-196 46 359. The pump forms a representative toothed rotor set consisting of an outer ring with an internal gearing and an eccentrically accommodated gear wheel with external gearing, whereby the internal gearing is formed by pivoted rollers in the outer ring and has one tooth more than the outer gearing, whereby the outer gearing of the gear wheel is a fine gearing with a basically smaller module superposed, and each roller has on its periphery a fine gearing with the same module into which the teeth of the geared wheel engage.
The function of the toothed rotor set becomes apparent in that a drive factor operates through a drive shaft on the inner rotor and rotates this. From the geared inner rotor, a force is transmitted to the planet pinion which on the one hand provides an impulsive force through the center of the planet rotor and a peripheral force which brings about a torque of the planet rotor. Owing to the impulsive force which acts on the ring bearing, this is put into rotation.
The forces and torque arising can not be optimally accommodated with the representative toothed rotor set through the previously used involute toothed system. There in particular exists the problem that the known gearing does not transmit the impulsive and peripheral forces without great surface pressure in the form of a linear contact. The previously known gearing systems are only suitable for the transmission of high peripheral forces and not for the transmission of great impulsive forces which run through the center of the planet rotor.
The model toothed rotor set proves to be disadvantageous in that a clean rolling out is not guaranteed under all operating conditions without engagement disturbances. The motion of the planet rotors relative to the ring bearing comes to a standstill in one position.
In this state in which the planet rotor almost stands still and at the same time a great force is transmitted, there exists the danger that the lubricant film between planet gear tip and outer rotor will break down, owing to which the Couette flow is brought to a standstill. Here a solid body contact arises through the loss of lubricant in the gap. There consequently no longer exists a favorable hydrodynamic lubrication but rather mixed friction states and in unfavorable cases a static friction. In the event of mixed and static friction, wear and tear phenomena arise and the service life of the toothed rotor set is reduced.
From U.S. Pat. No. 5,595,479, a hydraulic machine is known which is constructed from a rotable ring bearing with bearing pockets, whereby pivoted rollers with recesses are arranged in the bearing pockets on the peripheral surface, with an inner rotor mounted eccentrically toward the bearing ring with approximately star-shaped outer contour, whereby the points of the stars engage into the recesses of the rollers. The rollers and the inner rotor do not have the fine gearing of the invention, owing to which especially with toothed gear sets with a higher number of gear teeth, for example 11/12, engagement disturbances arise. The construction is only capable of running with very small tolerances.
From the disadvantages of the known state of the art, there results the objective of creating a toothed rotor set which is configured such that a lasting lubricant film structure for avoiding unfavorable friction states is guaranteed, whereby the toothed rotor set must safely transmit the forces and torque arising.
The object is accomplished in accordance with the invention though a toothed rotor set consisting of a rotatable ring bearing with bearing pockets in which pivoted planet rotors are arranged which form an inner gearing with an internal motor mounted eccentrically toward the ring bearing with approximately star-shaped outer contour which is provided with an outer contour, whereby the outer gearing has one tooth less than the inner gearing, and the gearing system of at least one of the two rotor systems has in part regions of the tooth form of the bearing an arch-like component. The advantage of a toothed rotor set configured in this way consists in that through the arch-like component in the tooth form, a rolling friction and no sliding friction occurs, so that the wear and tear on the gearing is minimized. Owing to the convexly constructed gear tooth tip of the geared internal rotor and the concavely constructed gear tooth root, there arises a contact surface and not a contact line. The Hertzian pressing is very greatly reduced through this roller pairing.
This also applies for the gear tooth flanks of the geared inner rotor and the geared planet rotor. By incorporating a flank play between the gear tooth of the planet rotor and the tooth gap of the inner rotor, it is guaranteed that the great impulsive forces are only transmitted through the gear tip and the gear tooth root. In this way, the action of great wedge forces acting on the gear tooth flanks is prevented, which can lead to the destruction of the flank surfaces. In addition, the flow medium can flow out of the gear tooth gaps owing to the flank play, as otherwise oil compression can arise which can lead to a very high pressure build up.
It is provided in an advantageous configuration of the invention, that the shape of the gear tooth is constructed arch-like in the region of the gear tooth tip and/or the gear root. Such a configuration of the tooth shape in the region of the gear tooth tip and/or the gear root makes it possible to be able to transmit very large impulsive forces (radial forces), whereby the portion of the peripheral force to be transmitted can be very small. In this connection, the gear tooth tip and the gear root are, in contrast involute toothed gear systems known in connection with toothed rotors, incorporated into the rolling off process, that is the hobbing of the geared planet rotor on the geared inner rotor curve.
The convexly curved gear tooth flank of the planet rotor and the concavely curved tooth flank of the inner rotor form a relatively large sealing area upon gear engagement which seals off the displacer chamber when the displacer chamber passes over from the suction region into the pressure region. Even deviations in the perpendicularity of the rotor do not lead to leakage losses of the displacer chamber.
It is provided in an advantageous configuration of the invention that especially [in] the region of the gear tooth tip and/or the gear foot, the gear tooth shape has a flattening. In the main zone of force transmission, in which the torque acts on the ring bearing through the geared inner rotor through the geared planet rotor, a standstill of the planet rotor almost occurs, geometrically conditioned. With the relative standstill described and the simultaneous transmission of a great force, there exists the danger that the lubricant film will break down between the planet tooth tip and the ring bearing ring. In order to counteract this, the planet rotor gear tooth tips were flattened. The magnitude of the flattening depends upon the usable area of the toothed rotor. At low rotational speeds and high pressures, a great flattening is necessary. At great rotational speeds and low pressures, a small flattening is necessary to guarantee a lubricating film build up even at low sliding speeds. For the transmission from the gear tooth tip of the planet rotor to the flattening, a special curve, a cycloid, is used, which more strongly promotes the lubricant film build up than a simple transition radius.
In a further advantageous configuration of the invention, it is provided that in particular in the region of the gear tooth tip and/or the gear toot, the shape of the tooth has a great curvature radius. Instead of a flattening, it is also appropriate to provide, in the region of the gear tooth tip and/or gear foot, a surface with a large curvature radius.
By flattening the planet rotor gear tooth tips, an improvement of force transmission (Hertzian pressing) by the planet rotor on the ring bearing is brought about.
In an especially advantageous configuration of the invention, it is provided that the arch-like component is constructed at least partially as a cycloid. The cycloid has proven to be especially advantageous in relation to the rolling off behavior and the transmission of impulsive forces. This cycloid gearing guarantees, even with considerable changes in curvature and small curvature radii, a trouble-free low-sliding rolling off which once again reduces wear and tear.
It is provided in an appropriate construction of the invention that at least in the region of the gear tooth flanks, the shape of the teeth is constructed as involuted. With this gearing system, the gear tooth flanks of the toothed inner rotor and the outer geared planet rotor are formed by an involute, whereby nevertheless in this embodiments, engagement disturbances can arise more easily that with an embodiment whose gear teeth flanks are constructed as cycloids.
It is provided in an advantageous configuration of the invention that the gearing has a low wear and tear surface. The low wear and tear surface can be obtained by a chemical, especially thermo-chemical and/or physical surface treatment. The surface can furthermore also be galvanized. Further advantageous surface treatment procedures are carbureting, nitrification and/or nitrocarbureting, borification and/or chrome sensitization.
It is provided in an appropriate configuration of the invention that, in the region of bearing pockets, at least one fluid channel is arranged. The fluid channel can be connected with the pump with the pressure side so that lubricating oil is continuously fed between planet rotor and bearing pocket in order to guarantee improved lubricating film build up.
Advantageously all moving parts of the toothed rotor set, especially the ring bearing and/or the planet rotors and/or the inner rotor have at least one circular bar on a face. This circular bar serves as sealing inside the housing in which the toothed rotor set is accommodated. Usually such moving parts have a sealing surface on their front sides which extend over their entire surface with exception of the gearing. This sealing of the invention by means of a circular bar has the advantage that the high friction forces arising with the known seals are strongly diminished and thus the toothed rotor set operates easier and therewith more efficiently. At the same time, the circular bar has a width which represents the optimum between sealing action and friction force.
Finally, the invention concerns a process for manufacturing a gearing rotor set whereby this is manufactured in a shaping process, preferably using a powder metallurgical process, plastic injection molding, cold forging, die casting, especially aluminum die casting, and stamping processes. An expensive gearing such as the toothed rotor set of the invention has can be produced simply and economically by means of this process. A filing and sawing, which as is well known is used with the usual gearing systems, can have no application in the present invention as the gearing for this is constructed in an excessively complicated manner.
In an advantageous configuration of the invention, it is provided that the toothed rotor set is used in a pump, especially a lubricating oil pump for internal combustion motors.
In a further advantageous configuration of the invention, it is provided that the toothed rotor set is used as a motor.